Our water pump has been starting by itself with no water being used for a couple of trip now. I have looked for a leak but cannot find one . We do empty the fresh tank so air probably gets introduced could this be the cause ?

Otherwise any tips on where to look for a leak ? If it is a leak it must be really small as I cannot find any water plus the pump only start every 20 mins or so for about 1 second.

Check the inlet fittings near the pump for a suction "air" leak, they may appear to be tight because of no water leak. Double check for suction "air" leak. Vibration of the pump running will cause the threaded fittings to become loose.

Just saw this thread. So being relatively new to the whole TT scene, your pump shouldn't be running at all when you don't have a faucet or the toilet running? Our pump will randomly turn on throughout the day and night. Even during the middle of the night. DH said it was normal. I would say its not, by reading this thread. Opinions? Solutions, etc.?

My vote is air isn't out of the system yet.
Every year I had this problem the first trip sometimes the second.
After that it was fine rest of the year.
Also if you have one check the strainer bowl by the pump.
I'm sure herk has a pic.
Mine was loose this year causing the pump to run once and awhile.
check low point drain caps to.

A water leak will also cause the pump to cycle, worse the leak, more often. Old trailer, a couple of seconds every couple of hours, new trailer not at all until the valve fell apart for the outside shower. Got it back together best I could, was once an hour or so and got more frequent as time went on. No problems since I replaced the valve. Wayne

Timely I originally posted this thread. Took our pump apart last night, the check valve was passing. It is an integral part of the pump, simple fix took it all apart cleaned the seat on the PTFE disc and then simply put a really small spacer behind the spring to slightly increase the seal pressure when I blow backwards pump no longer passes !!!
Will put it back in the trailer tonight and check it all works.